Periscope
an instrument for observation from a concealed position. In its most elementary form it is a tube in each end of which are reflecting surfaces set parallel to each other at an angle of 45° with the axis of the tube. This form of periscope, with the addition of a simple lens, was much used for observation purposes in the trenches during the World War.
HOOD (A)OBJECTIVE (PL) PRISM (9) LENS (U)LENS INNER TUBE (U2) LENS OUTER TUBE (B)210 1 GEARING (02) LENS (PA) LENS AND ERECTING PRISM WHEEL FOR ROTATING TUBE ΕΥΕ (02) PIECE DIAGRAM OF PERISCOPE The principle of the periscope of a submarine is essentially the same-reflecting prisms and several lenses are used, and a collecting eye piece is placed at the lower end. This type of periscope is protected by a casing tube and head.
A system of gears is used to turn the inner tube, in order that it may be trained upon a desired point.
Although the periscope in some form comparatively recent. ment into an efficient instrument has been known for centuries, its development into an efficient instrument has been comparatively recent. feet in all but the Tapiridx and the Bronfication, a hind feet are odd toed in all, and the fore section of Ungulata. The feet in all but the Tapiridæ and the Bron- PERITONITIS fluid, like the liquid white of an egg, allowing the two sides, when rubbed totion. The outside of this is rough and ner and outer sides of this immense bag granulated. The peculiarity of the ingether, to glide over each other, as if lies in this, that the surface of the first oiled, without check or the slightest fric- Usually there is but one horn; if two are except in the extinct Diceratherium. chanter. Horns, if present, not paired, less than 23. Femur with a third trochanter. Horns, if present, not paired, except in the extinct Diceratherium.
Usually there is but one horn; if two are present, they are in the median line of the head, one behind the other, not supported by bony horn cores. is now usually divided into seven families, four extinct. The section however firmly pressed, can never grow together, or keep long in contact; while that of the other is rough, dry, and adheres firmly to all with which it comes in that of the other is rough, dry, and ad- together, or keep long in contact; while however firmly pressed, can never grow contact. This external side, then, adheres to the muscles of the abd such a manner that between every conto every portion of the intestines, but in abdomen, and volution, or twist of the bowels, a fold such a manner that between every con- to every portion of the intestines, but in heres to the muscles of the abdomen, and PERISCOPE DIAGRAM OF SUBMARINE SHOWING POSITION OF PERISCOPE